Comet 46P/Wirtanen

On December 18th, 2018, Comet 46P/Wirtanen was naked eye visible from my backyard.  Just barely.  

If you waited for moonset and knew exactly where to look and used averted vision.  Yup.  There it was.  A dim grayish-green splotch in the sky.

It was even better when looking through binoculars.  It became a dim green blob.

Then, I aimed the 10 inch Dob at it.  It became a much bigger, brighter, but still dim green blob, but now with the increased aperture and magnification, I could see the comet's motion against the starfield.

Using the ZWO ASI294MC imager, I captured this.

46P Zooming by

This data was captured and live stacked with SharpCap.  It's 151 frames at 8 seconds exposure, each.  So, basically, this is a 20 minute exposure with the starfield being tracked so the relative motion of the comet is apparent.

What if I wanted to track the comet instead of the starfield?  It turns out that is a much harder problem.  The scope only has tracking modes for lunar, solar, and sidereal.

This was a perfect time to gather data and give DeepSkyStacker a try! 

With the data, I could use DeepSkyStacker for post processing.

I captured over 500 frames of comet data during this session.  That ate a lot of room on the hard drive. Clearly, it is now time to increase the size of the storage in the astro laptop.  That'll be the subject of a future blog post.

With DeepSkyStacker, I had to mark the comet's position in each one of the data frames.  That was pretty tedious, but afterwards I found that it could be done algorithmically if the frames have an embedded date and time stamp. 

With that done, I started the stacking process.

Hours later, and with some tweaking, this is the best I could do.

46P Zooming by

The stacked brilliance of the comet swamps the resultant image and color is missing, but you can see the streaks of the starfield!

I will continue to use DeepSkyStacker for post processing data throughout the upcoming year.  Who knows what new things I'll learn?